TOPIC: Low Water Pressure Alarm?

Guys,

I have a water pressure gauge on my '63 Merc 850, and if I am looking at it I can see there is sufficient water pressure to cool my motor. As with all outoards there is a telltail where I can see if its pumping water. The problem is that when I am rocketing around at WOT I can only glance at the gauge from time to time, and I never turn my head around to see the telltail. What I want is a loud alarm to go off when the water pump fails to deliver minimum pressure.

I have high temp alarms on my inboard boat's engines, and I know the newer computerized outboards (like my Etec 50) have alarms and will even automatically slow down the engine if it overheats. But I want assurance that I'm not going to fry my motor... which it seems a lot old dead outboards have. I expect that high temp alarm isnt sufficient for an outboard, in that once it overheats at WOT, its too late, the damage is done... and this could take only a few 10s of seconds at WOT.

In a previous life, I was an instrumentation guy, and I could whip up a low pressure switch to put inline with my pressure gauge (connected to 12 VDC and a >100dB audible alarm).

I have two questions; are there low pressure alarms for outboards already out there available that I could buy? and if not, and I took the time to design and build one, is this something that would be of interest to others?

Murphy makes a line of "Switchgauge" meters Dean, they have them with the range as low as 15 or 30 psi, adjustable alarm setting at 3-7 psi. (Not specifically marine, but may be of interest.)
www.fwmurphy.com/20p_25p/

Thanks Mark! This looks like the ticket.

I am a little concerned about the 3 psi trip point. I pull my water pressure from the top of the inline 6 block (thats where I had a NPT plug) and my gauge indicates only 1-2 lbs at slow idle... It could be my gauge isnt accurate at the low pressures... i just dont want the alarm going off when I'm going slow.

I found a pressure switch (no gauge) that can be set between 0.5 and 2 lbs pressure ($20). I am thinking with this kind of switch, I could just mount the switch and the alarm under the hood of the motor.

www.newark.com/jsp/search/productdetail.jsp?id=24R7137&Ntt=PSF102-7651-713
www.farnell.com/datasheets/515831.pdf

If you have problems at lower rpm's you might be able to find a mini time-delay relay to cut off the buzzer after so many seconds, could also have a switch the linkage trips at near idle to cut the buzzer?